Nickel (Ni) is an essential micronutrient known for improving the growth and yield of various crops at low concentrations. However, the nickel’s adequate information on shallots is insufficient. This study found out the effect of Ni fertilization with four concentrations (0.0, 0.025, 0.1, and 0.4 mg L^-1 derived from NiSO4.6H2O) on plant and bulb weight, nutrient solution usage, and bulb nickel and nitrate content of two shallot cultivars (Lokananta and Sanren F1) using hydroponic condition, arranged in a split-plot design under field conditions. Increased Ni concentration (0.4 mg L^-1) negatively affected plant height, total plant weight, bulb weight per plant, and total nutrient solution usage, while it increased the bulb nickel and leaf carotenoid contents. The Ni concentration (0.025 mg L^-1) can be safer for shallot plant absorption with optimum growth and yield. Shallot cultivar Sanren F1 provides considerably better results in terms of yield components than cultivar Lokananta. Bulb weight per plant appeared positively correlated with the number of leaves, bulbs, total bulb diameter, and total volume of nutrient solution used per plant. The total bulb diameter per plant showed a better direct effect on the shallot bulb yield at various Ni levels.

Keywords: Shallot (Allium cepa L. Aggregatum group), cultivars, Ni nutrition, growth, physiological components, yield traits, path analysis, Pearson’s correlation

Key findings: Ni at a low concentration (0.025 mg L^-1) stimulates the growth and physiological components of shallot plants, which, in turn, increases bulb yield. Leaf carotenoid content and water uptake can assess the response of shallot plants to heavy metal stress conditions.